Implement ADCP Async Execution Model with Handler-Controlled Flow (PR #78)

[bokelley]

Summary

Implements a comprehensive async execution model for the ADCP TypeScript client library based on ADCP spec PR #78. This introduces handler-controlled flow with four clear async status patterns, replacing the previous complex configuration system with a simplified, spec-compliant approach.

Key Features

• Handler-Controlled Flow: Input handlers are now mandatory for input-required status, providing explicit control over async execution
• Four Clear Async Patterns:

• completed (0-2s): Immediate task completion
• working (2s-120s): Server processing with SSE connection
• submitted (hours-days): Long-running tasks with webhook notifications
• input-required: Handler provides clarification responses
  • Type-Safe Continuations: DeferredContinuation and SubmittedContinuation preserve TypeScript types through async boundaries
  • Client vs Server Async Distinction: Client deferrals don't use webhooks, only server async processing does

Breaking Changes

• Input handlers are now mandatory for input-required status (no automatic deferral)
• Removed complex configuration options in favor of ADCP spec compliance
• Updated error handling for new async patterns (InputRequiredError, ClarificationTimeoutError)
• Protocol detection simplified to follow ADCP spec exactly

Implementation Details

Core Changes:

• TaskExecutor: Complete rewrite with handleAsyncResponse() method
• ProtocolResponseParser: Simplified to check status === 'input-required' directly
• ConversationTypes: Added async continuation interfaces
• ADCPClient/MultiAgentClient: Updated to support input handlers

New Async Flow:

1. Task execution returns TaskResult<T> with status-specific responses
2. For input-required: handler is called with conversation context
3. Handler can provide immediate input or defer for human approval
4. For working/submitted: appropriate continuation objects manage async operations

Documentation

• Migration Guide: Step-by-step guide for existing users
• Developer Guide: Comprehensive coverage of all async patterns
• Handler Patterns Guide: Advanced implementation strategies and best practices
• Real-World Examples: Production-ready use cases and patterns
• Troubleshooting Guide: Diagnostic tools and common issues
• API Reference: Complete TypeScript definitions and interfaces

Testing

• Comprehensive Test Suite: 6 new test files covering all async patterns
• Handler Testing: Validation of handler-controlled flow
• Error Scenarios: Complete error handling verification
• Type Safety: TypeScript type preservation testing
• Mock Strategies: Unit testing approaches for async patterns

Performance & Reliability

• Optimized Protocol Detection: Removed unnecessary complexity
• Memory Management: Proper cleanup of async operations
• Error Recovery: Robust error handling for all failure scenarios
• Connection Management: Efficient SSE and webhook handling

Test Plan

• All existing tests pass
• New async pattern tests pass
• TypeScript compilation successful
• Handler-controlled flow validation
• Error scenario testing
• Type safety verification
• Documentation examples work correctly

Migration Impact

This is a significant but well-documented breaking change. The migration guide provides:

• Step-by-step migration instructions
• Before/after code examples
• Gradual migration strategies for production systems
• Common pattern transformations

Expert Reviews

✅ javascript-protocol-expert: Approved implementation and async patterns
✅ nodejs-testing-expert: Validated testing strategy and mock approaches
✅ docs-expert: Created comprehensive documentation suite

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